As consumer-oriented angular-velocity sensors, so-called vibratory gyrosensors are widely used. A vibratory gyrosensor detects an angular velocity by allowing a cantilever vibrator to vibrate at a predetermined resonant frequency, and then detecting a Coriolis force produced in response to an effect of angular velocity using a piezoelectric element.
Vibratory gyrosensors are advantageous in having a simple mechanism, short activation time, and low manufacturing cost. For example, vibratory gyrosensors are incorporated in electronic devices, such as video cameras, virtual reality devices, and car navigation systems, so as to function as sensors for motion-blur detection, motion detection, and direction finding, respectively.
A typical vibratory gyrosensor includes a vibration element which is manufactured by machine-cutting an appropriate piezoelectric material into a predetermined shape. With reduction in size and weight and improvements in functionality and performance of a main apparatus in which a vibratory gyrosensor is to be incorporated, a vibratory gyrosensor requires a smaller size and higher performance. However, it is difficult to manufacture a small vibration element with high precision due to limitations in machining accuracy.
Recently, there has been proposed a vibratory gyrosensor including a cantilever vibration element that is formed by laminating a pair of electrode layers with a piezoelectric thin film layer interposed therebetween on a silicon substrate by means of a thin film technique used in semiconductor processes (for example, see Patent Document 1). Such a vibratory gyrosensor achieves reduction in size and thickness and can thus be combined with a sensor used for other purposes, thereby achieving composition and higher functionality.
With the reduction in size and weight and improvements in functionality and performance of an apparatus in which a vibratory gyrosensor is to be incorporated, a vibratory gyrosensor requires a smaller size and higher performance. For example, by combining a vibratory gyrosensor with another type of sensor, multi-functionality is achieved. Moreover, in the vibratory gyrosensor, the vibration element is mounted on the supporting substrate, and the vibratory gyrosensor is mounted on a control substrate of the main apparatus together with the another type of sensor, thereby achieving size reduction as a whole.
However, in the typical vibratory gyrosensor, the electrodes of the vibration element and terminals provided on the supporting substrate are generally connected to each other by wire bonding. This means that a space is required around the periphery of the vibration element so that the wires can extend within the space. This space is one of the factors that interfere with an achievement of size reduction.
Furthermore, due to the size reduction, a vibratory gyrosensor may be significantly affected by, for example, vibration from the outside. This may be problematic in leading to an increase in cost as the supporting structure for the vibration element becomes more complex. Although an installation condition of a vibratory gyrosensor is determined based on specifications of the apparatus, it is required that predetermined characteristics be stably attained under any condition. In order to attain stable characteristics with high sensitivity in a vibratory gyrosensor, a mechanical quality coefficient Q value (Q factor), which determines the resonant state of the vibration element, must be increased. A mechanical quality coefficient Q value is determined on the basis of the material of the vibration element and the securing structure for the vibration element.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 7-113643